Instrument for measuring speed of shafts and the like



J. N. CORRY Aug. 18, 1953 INSTRUMENT FOR MEASURING SPEED OF SHAFTS, AND THE LIKE Filed Se t. 14, 1948 2 Sheets-Sheet 1 I0 I I r E EE mvsnToR .N. ORRY fi c 1%.

A'r'rYS J. N. CORRY Aug. 18, 1953 INSTRUMENT FOR MEASURING SPEED OF SHAFTS, AND THE LIKE Filed Sept. 14, 1948 2 Sheets-Sheet 2 mvENToR J. N..CORRY jyl Patented Aug. 18, 1953 UNITED STATES ATENT OFFICE INSTRUMENT FOR MEASURING SPEED OF SHAFTS AND THE LIKE This invention relates to a device for measuring the speed of revolution of shafts and the like.

A great demand exists for a revolution counter which can be sold at a low price.

The device of my invention is designed to mac this demand, and in order to accomplish this objective I have made use of a mode of measurement which I believe to be new in the field of revolution indicators. The mode of measurement which I employ is that of a freely mounted shaft carrying a flywheel which is given a speed of rotation which is related to the speed of rotation which is to be measured. The shaft is then halted and the stored energy of the fly-wheel is expended against the action of a spring. It will be apparent that the kinetic energy of the wheel will vary as the square of its angular velocity since its mass is constant. Evidently, it is only necessary to measure the effect upon the spring of the kinetic energy expended by the flywheel. This effect, then, is measured. I prefer to make this measurement so as to obtain directly at figure representing revolutions per unit time.

In addition to the provision of a low priced device for measuring speed of revolution, it is a further object of the invention to provide a device which may be used to measure the speed of shafts and the like without the necessity of bringe A ing the device into direct contact with the shaft in question.

It is a further object of the invention to provide a device which gives a direct reading or which gives a reading which need only be multiplied by a simple number to obtain the revolutions per unit time.

With these and other objects in view, my invention generally comprises a frame, a shaft freely mounted. in said frame, a fly-wheel rigidly mounted upon said shaft, means for bringing said shaft up to the desired speed, means for halting said shaft, a spring mounted so as to be distorted by the energy stored in said fly-wheel at the time said shaft is halted, and an indicating means designed to record the degree of distortion of said spring.

In order to illustrate my invention, I intend to;

describe in detail, and show drawings of, on e deprovided with a scale ll.

vice in accordance with my invention. I have chosen to illustrate the case when a torsion spring is employed. However, I do not intend that the invention should be limited to this one device since it is merely being shownas one example of how the invention may be applied.

In the drawings:

Figure l is a sectional view of the device taken through the centre thereof.

Figure 2 shows a means for turning the shaft when direct contact with the shaft of unknown speed is not being used.

Figure 3 shows a stroboscopic disc mounted on the fly-wheel. (The remainder of the device is not shown.) This disc is used, as in the case of the means shown in Figure 2, when direct contact with the shaft of unknown speed is not being used.

Figure 4 is a fragmentary view of a means for halting rotation of theshaft, taken along the line 4-4 of Figure 1.

Figure 5 is a fragmentary view of a means for moving the indicating arm relative to the flywheel during the halting of the shaft, taken along the line 55 of Figure 1.

Throughout the several figures, like reference numerals refer to like parts. In the embodiment, of the invention illustrated in the drawings, reference numeral Ill indicates a frame for the instrument made up of rectangular end pieces ii 'joined by cross members l2.

An anti-friction bearing, preferably in the form of a ball bearing assembly I3, is mounted in an orifice in each end piece 1 I. A shaft I4 is mounted by ball bearing assemblies [3 so as to be freely rotatable relative to frame Ill. Each end of shaft M projects beyond end pieces ll. Each end of shaft M is provided with a rubber tip i 5. Rigidly secured to shaft 14 exteriorly of frame II], is a fly-wheel H5. The periphery of fly-wheel I5 is g A hub i8 is mounted on shaft l4 rearwardly of fly-wheel l6. Hub 5% has a projecting portion Ida extending rearwardly thereof. A set screw l9 secures hub l8 upon shaft 14. A second hub 20 is rotatably mounted upon part of the projecting portion l8a of hub I8. Hub 29 carries a rigidly connected indicating arm 2i and a disc cam 22. A spring element 23, which is preferably made of Phosphor bronze, is freely mounted upon projecting portion iBa of hub member [8. Portions of spring member 23 are in frictional contact with disc cam 22. The end of the projecting portion [8a is externally screw threaded and an adjusting nut 2t is mountedupon this thread, said nutbeingprovided to vary 3 th amount of frictional contact between spring eiement 23 and disc cam 22. Adjusting nut 24 is locked in position by means of a lock nut 25.

Rigidly mounted upon shaft bl, between end pieces H, is a hub 2i which is fixed to shaft I 3 by means of a pin 28. Freely mounted upon shaft it between one end piece I! and hub 2'! is a sleeve 29 carrying a disc cam 30. A torsion spring 3i is concentrically wound upon sleeve 29, one end of said spring being connected to disc cam 38, the other end of said spring being connected to hub 23. Disc cam 30 is provided with a rise 32 and a drop 33. An arm 34 is rigidly mounted upon a shaft 34a, and shaft 3 a is rotatably mounted by the end pieces l l. A sprin 35 is operatively connected with arm 3 5, tending to cause arm .33 to rotate downwardly, A spring loaded trigger release mechanism 36 is mounted upon end piece H and is adapted to hold arm a out of contact with disc cam 35. When, however, trigger release mechanism 36 is tripped, arm 34 rotates downwardly and bears against disc cam Bil. Arm 34 may be employed to stop rotation of disc cam 36 due to the entrance of arm 34 in the drop 33 in the said disc cam. This operation will be effective only when disc earn as is rotating in one predetermined direction, which direction will be determined by the manner in which rise 32 and drop 33 are struck in disc cam 38.

When shaft H3 is rotating in a direction in which arm 34 is effective in halting disc cam 36, then the application of arm 34 so as to engage drop 33 will not only halt disc cam 33 but will also, in time, halt shaft I4. Shaft M will be halted since torsion sprin Si is connected both to disc cam 30 and hub 27 which is secured to shaft M. Therefore, rotation of shaft it after application of arm 3% in drop 33 is only possible against the action of torsion spring 3i, and such action will necessarily cause temporary distortion of spring 3|.

The projecting end of shaft 34a (on the flywheel side of end piece ll) carries an arm 193 of resilient material such as spring steel. A member 40a is attached to substantially the mid point of arm is. Disc cam 22 is provided with a rise ii and a drop (22. Arm as is designed to cooperate with drop 42 and checl; the rotation of disc cam 22 contemporaneously with the stoppage of disc cam 38 by meansof arm 35. Since indicating arm 2! is carried by the hub 2b (which also carries disc cam 22) the stoppage of disc cam 22 causes relative movement to take place between halted indicator arm 2! and scale 1'! on fly-wheel It. This movement takes place despite the frictional contact of hub 20 and hub it (which contact is brought about by the pressure of spring element 23).

in one direction, the fly wheel will then rotate in the opposite direction, but, during this secend-mentioned rotation, indicator arm 2! will not change position relative to scale i1, due to the frictional contact imposed by spring element 23 between hubs l3 and 20. Arm i0 and drop d2 act to overcome this frictional contact only when disc cam 22 is rotating in one predetermined direction, which directionis the same as that in which arm 34 operates to halt disc cam so. When it is desired to return indicating arm 25 to the zero position on scale [1, arm 34 is rotated upwardly so as to be held by trigger release mechanism 36. Member 40a is then pressed upwardly causing arm 20 to flex downwardly, whereby arm 40 engages drop 42 in disc cam 22.

When torsion spring H has caused the fly-wheel to cease to rotate d Shaft M is then rotated until indicating arm 2| is at the zero position on scale l1.

When it is desired to get shaft M rotating at the same speed as the shaft of unknown speed, this may be simply done by pressing either of the rubber tips is against the end of the shaft of unknown speed. Since the device can only be stopped by means of arm 2%; when it is rotating in one predetermined direction, then the rubber tip 55 must be chosen which will give the desired predetermined direction of rotation to shaft Hi.

When it is desired to obtain a reading of revolutions per unit time of a shaft or the like, and it is either impossible or difficult to place the instrument directly against the shaft, I employ the stroboscopic principle to relate the speed of shaft it with the speed of the unknown shaft. A wheel :33, preferably made of rubber or like material is rotatably mounted upon an a l which is pivotally mounted upon end piece H as shown at 55. A spring member -ili, also mounted upon end piece ll, normally holds arm at, carrying wheel 43, away from shaft 5%. A stop ll limits the distance which spring ii-3 holds wheel 43 away from shaft id. Wheel 63 may be rotated with the palm of the hand and pressed inwardly so as to frictionally engage shaft it and rotate the latter. Wheel 45, is of much greater diameter than shaft M. It is, therefore, possible to rotate and press inwardly wheel 53 and thus impart the desired speed to shaft 4.

Fly-wheel it is provided with a number of orifices G8 and a cardboard disc 59 having orifices 58 therein is mounted upon fly-wheel l6. Disc 49 is so located on fly-wheel it that vision is permitted through at least one of the orifices 48, due to the fact that at least one orifice 56 overlies one orifice Q8. The end of the shaft of unknown speed is provided with suitable markings. These markings are then sighted through the exposed orifices in fly wheel 16. In operation, the speed of fly wheel !5 is brought up to a speed slightly in excess of that speed of the observed shaft at which the markings on the latter appear to be stationary, and is then allowed to slow down until the markings appear stationary. A revolutions per unit time'reading is then taken with the device of my invention. The speed of the shaft under observation may then be found by application of the following formula:

Indicated revolutions per unit time multiplied by the number of exposed orifices in the fly-wheel and divided by the number of images. By number of images I means the number of times a single marking on the shaft under observation is seen through all the exposed orifices in the fly-wheel of the adjusted to speed shaft it.

To take a reading of revolutions per unit time with the device of my invention, it is only necessary to bring the shaft up to the desired speed in either of the fashions indicated above. Then arm 34 is released by the tripping of trigger release mechanism 3%. Arm 3% enters rise in disc cam 38 and disc cam Eli is halted. Meanwhile, the stored energy of fly--wheel it causes it to continue to rotate against the action of torsion spring 3|. During this rotation of the fly-wheel, indicating arm 25 is given a movement relative to the scale ll. When maximum distortion occurs, the fly-wheel changes its direction of rotation and may be allowed to come to a halt or may be halted. A reading is then taken upon Modifications of this invention will be apparent to those skilled in the mechanical arts and in the art of instrument making. It is, therefore, intended that the scope of this invention should be limited only by the nature of the subjoined claims.

What I claim as my invention is:

l. A device for measuring the speed of shafts and the like comprising a frame, anti-friction bearings mounted on said frame, a shaft mounted in said anti-friction bearings, said shaft having each of its ends projecting outwardly from said frame, a fly-wheel rigidly mounted upon said shaft exteriorly of said frame, means for rotating said shaft, a hub rigidly secured to said shaft, a sleeve carrying a disc cam freely mounted upon said shaft, a torsion spring substantially concentrically mounted upon said shaft, one end of said spring being secured to said hub, the other end of said spring being secured to said disc cam, an arm mounted upon said frame and adapted to cooperate with said disc cam so as to halt the latter, said arm being normally held out of engagement with said disc cam by means of a trigger release mechanism, said arm being releasable by tripping of said trigger release mechanism so as to engage said disc cam, and indicating means designed to measure the maximum amount of distortion imparted to said spring after tripping of said trigger release mechanism.

2. A device for measuring the speed of shafts and the like as described in claim 1 in which said means for rotating said shaft comprises a Wheel rotatably mounted upon an arm, said arm being pivotally mounted on said frame, and in which a plurality of orifices are disposed in said flywheel in order that the latter may be employed to stroboscopically establish a relationship between the speed of said shaft and the speed of the shaft being observed.

JOHN NIELSON CORRY.

References Cited in the file Of this patent UNITED STATES PATENTS Number Name Date 1,024,183 Clinker Apr. 23, 1912 ,022,666 Haskell Dec. 3, 1935 ,177,876 Perrey Oct. 31, 1939 2,193,646 Rich Mar. 12, 1940 2,342,141 Hansen Feb. 22, 1944 2,427,796 Macdonald Sept. 23, 1947 

